To specify a suitable prior, we assume that observational data alone should remain uninformative about \(h\) , i.e. that \(Q(h | x, y, n) = Q(h)\)This assumption is not innocent, as it is violated in work which assumes the causal orientation can be identified from observational data  [1]}. This could be implemented by specifying (\(P(x|y, h)\) , \(P(y|h)\)  \(P(x|y, h)\) ) and (\(P(x|y, \lnot h)\) , \(P(x|\lnot h)\) ) separately.. To ensure this, we must have
\(Q(y | h, x, n)Q(x|n, h) = Q(y | \lnot h, x, n)Q(x|n, \lnot h)\) 
